Two-stage holding magnet for presses and the like



July 18, 1961 w. STOLK ETAL TWOSTAGE HOLDING MAGNET FOR PRESSES AND THELIKE Filed Aug. 16, 1956 2 Sheets-Sheet 1 w s m R J 5 0 y T Mm M vm m 1W55 v No r. MM/ W n W Y 5 July 18, 1961 w. STOLK ETAL TWO-STAGE HOLDINGMAGNET FOR PRESSES AND THE LIKE Filed Aug. 16, 1956 2 Sheets-Sheet 2 5 hM E TKO m w I 5 0 MN W I 0 E United States Patent 2,992,580 V TWO-STAGEHOLDING MAGNET FOR PRESSES AND THE LIKE William Stolk and Edward E.Judge, Jr., Lansing, M1ch.,

assignors to Machine Tool Electric Corporation, Lansing, Mich., acorporation of Michigan Filed Aug. 16, 1956, Ser. No. 604,507 12 Claims.(Cl. 83-136) The present invention relates to an improved magnetictwo-stage or dual acting holding unit for industrial presses and thelike, which is employed in the handling and disposal of scrap materialleft in the blanking out of pieces from an advancing strip of magneticmetal stock.

It has been been proposed to employ magnetic holding means inassociation with the moving die of a metal punching or stamping pressfor the purpose of retaining the stock from which a blank is struck outand of disposing of this scrap in a suitable receptacle.Electromagnetically energized units are employed for this purpose;however, it has been found that residual magnetism prevents theexpeditious discharge of the scrap to the receptacle, the magneticholding unit acting in the manner of a permanent magnet. Other types ofprovisions for stripping and discharging the scrap material, as by anair blast, mechanical stripping and handling means, and the like, arerelatively cumbersome and expensive.

It is therefore a general object of the invention to provide a two-stageor dual acting holding unit for the purpose described, in which aprimary electromagnet is energized as the moving die of the presspunches a part from a strip of ferrous metal, the magnet engaging andretaining the scrap left as the punched piece drops to a suitablereceiver, the primary magnet being de-energized following this; and inwhich auxiliary electromagnetically operated means of the improved unitthen acts mechanically to discharge the scrap into a suitable receptacleWhich has been advanced into receiving position in the meantime.

Another object is to provide an improved dual acting electromagneticscrap holding and handling unit of the type described, featuring aprimary holding electromagnet and an associated electromagnetic stripperacting in the manner of a solenoid to discharge the scrap in a positivefashion, in which the electromagnetic provisions are mounted in a verycompact manner for installation in a set along an edge of thereciprocating die of a press.

Another object of the invention is to provide an improvement in punchingor stamping presses having in combination therewith a dual actingmagnetic holding unit, or a set of such units, as described.

Yet another object is to provide an improved method of handling andstripping scrap stock as an incident in an industrial stampingoperation.

The foregoing as well as other objects will be made more apparent asthis description proceeds, especially when considered in connection withthe accompanying drawings, wherein:

FIG. 1 is a fragmentary view in vertical section through an improvedelectromagentic holding unit according to the invention, this view beingin section along a broken line corresponding to the line 11 of FIG. 2,and showing in a general way the manner of attaching it to a pressmember; I

FIGS. 2 and 3 are, respectively, top and bottom plan views of the unit;7

FIG. 4 is a fragmentary perspective view, schematic in nature,illustrating operations in the improved scrap holding and handlingmethod;

, FIG. 5 is a schematic fragmentary view in end elevation of thestructure of FIG. 4,.only'a single holding unit of a set being shown;

FIG. 6 is a wiring diagram. for the electromagnetic holding apparatus;and

FIG. 7 is a fragmentary plan view conventionally illustrating successivesteps in the performance of the method.

Referring first to FIGS. 1, 2 and 3, there is illustrated therein a dualacting electromagnetic holding unit 10 according to the invention, asoperatively applied to a vertically acting die member 11 of aconventional punch press, a set of units 10 being disposed along an edgeof the die beneath which a sheet or strip of magnetic metal stock issuccessively advanced as blanks are punched from the stock by a die (notshown) on the member 11, and in horizontally offset relation to such dieand a blank punched from the stock. Further reference, in general, tothe press and its operation in relation to the proposed method ofholding and handling scrap pieces will be hereinafter made.

The unit 10 includes a lower magnet housing 12 having a lower facesubstantially flush with that of die member 11, and an annular space 13receiving an electromagnet coil 14, the housing 12 being of magnetizablematerial and constituting the electromagnet core. A flange 15 extendsradially outwardly from the housing 12 about a portion of its periphery(FIGS. 2 and 3) and is apertured to receive bolts 16 by which the unit10 is secured on the die member 11 in horizontally or laterally offsetrelation to a die (not shown) carried by that member, i.e., laterally ortransversely of the direction of axial movement of such die, and of ablank B punched by the latter.

The annular coil receiving space 13 is closed off at its bottom by acentrally apertured spacer disk 17 of insulating material, held in placeby a split retaining ring 18, and the housing member 12 is provided withan upper opening 19 to this space for the accommodation of wiring (notshown) for the coil 14.

=Diametrically opposed bores 20 are for-med through the central coremember of the housing 12, on either side of the axis thereof, for thereception of like ejector or stripper pins 21, whose slightly enlargedheads 22 project upwardly into the central circular recess 23 of aninsulating spacer disk 24. This disk is secured on the housing 12 bycircumferentially spaced screws 25. As illustrated in FIG. 1, thebottoms of stripper pins 21 are in their inoperative, withdrawn positionat least substantially flush or upwardly within the lower face of diemember 11 and magnet housing 12.

The reference numeral 26 generally designates a solenoid housing ofcylindrical outline, substantially coextensive in diameter with thespacer 24 and electromagnet housing 12, and the housing 26 is secured inrelation to those parts by screws 27 connecting the solenoid housing 26to the insulating spacer disk 24.

The inner wall 28 of solenoid housing 26 is cylindrical, and the lower,radially flanged base of a fixed tubular solenoid core plate 29 isfitted in the interior of the housing 26. A further tubular, axiallymovable solenoid core 30 is spaced above the axial sleeve portion 31 ofthe member 29, in axial alignment therewith, and the core 30 slidesaxially in the radially flanged insulating spool 32 of a solenoid whosecoil 33 is housed between the spool flanges. A smallpin 34 preventsrotation of the stationary core plate 29 in reference to the spacer 24therebeneath. Rotation of the movable core 30 is prevented by "aradially extending pin 35 in the top wall of solenoid housing 26, thepin extending into an axial groove or slot 36 at the top of the core 30,which core projects through the top wall of the housing.

'j The axial bore 37 of core 30 adjustably receives the stem of anelongated plunger 39 provided with an enlarged tappet plate 40 at itslower end, which plate is received in the central opening 23 of spacer24. A threaded upper portion 41 of the plunger stem threadedly engagesan upper, reduced diameter portion of the bore 37, and is provided witha kerf or slot 42 to receive an adjusting tool. Thus, upon rotation ofthe stem plunger 39 in relation to core 30 the stroke of plunger tappet40, and the stripper pins 21 actuated thereby, may be adjusted. Acapstan type lock nut 43 is applied to the plunger above the tubularcore 30.

An electrical connector or fitting 44 leads to solenoid wiring space 45within the housing 26, which has a lateral access opening 46 normallyclosed by an arcuate plate 47. An insulating guide and spacer ring 48slidably receives the core 30 inwardly of the wiring space 45.

It is believed that the operation of the improved magnet unit willappear from the foregoing description. As the die member 11 and stripperhousing 12 descend to engage the sheet metal blank, the stripper pins21, in also engaging the sheet, will be elevated and withdrawn withinthe housing, since the solenoid coil 33 is de-energized at this time.Upon electrical energization of the coil 14, as through the circuitappearing in FIG. 6, the magnetic scrap material will be attracted toand held on the magnet housing 12, as the part or piece punched by a dieon the die member 11 is discharged to a suitable receiver. Uponinterposition of a scrap receiver beneath the die member and subsequentde-energization of electro-magnet coil 14 and energization of thesolenoid coil 33, the core 30 will be projected downwardly, carrying thestem 39 and its tappet plate 40, and thus causing the stripper pins 21to be projected a short distance of, say, A inch, out of the bottom ofthe housing 12. The scrap is thus ejected in a positive fashion from thepreviously magnetized housing 12. These operations are appropriatelycoordinated with the press die stroke, as by limit switch means, such asare shown in FIG. 6, as will be hereinafter referred to.

FIGS. 4, and 7 show in the most general way the mode of mounting a setof, say, six of the dual acting electromagnet units shown in FIGS. 1, 2and 3 on and along an edge of the moving die member 11 of a punch presswhose fixed base is designated 50, the remainder of the press body beingdesignated 51. All of the parts are quited conventional. The referencenumeral 52 represents a strip of blank material advancing endwisethrough the press, as viewed in FIG. 5; while a reciprocable scrapreceiver pan is conventionally shown and designated 53.

Referring to FIG. 7, a blank B is punched from the stock 52 at eachoperation of the die member 11, which also severs the stock between thepunched out margin and the sides of the stock, as at 54. Dotted lineportions of FIG. 7 represent a series of blank punching and scrapholding relationships corresponding to those shown in solid line, butperform subsequently at the same working station.

As shown in FIGS. 5, 6 and 7, the sequence of operations in accordancewith the new method is as follows: the stock 52 is advanced beneath thedie member 11 in the usual fashion, the member 11 descends to blank thepiece B, which falls into a receptacle in the lower press body 50, andthe electromagnet coil 14 is coincidentally energized by a limit switch,causing the severed scrap piece (55 in FIG. 7) to be attracted to andheld by the housing 12 of the set of electromagnetic units 10 arrangedalong the face of the die. The die member 11 then raises to its startingposition, carrying with it the scrap 55, whereupon the scrap receiver,tray or pan 53 is projected laterally beneath the die member. Solenoidcoil 33 of the unit 10 is now energized by limit switch means,simultaneously with the de-energization of the electromagnet coil 14,causing the stripper pins 21 to be projected downwardly as abovedescribed. They en gage the scrap piece 55 and kick it off the magnethousing '12 into the receiver 53, which is then reversed in movement andextracted from beneath the die member '11. The above sequence ofoperations then repeats.

Referring to the schematic diagram of FIG. 6, the wiring arrangement isbelieved self-explanatory, in the main. A step-down transformer 56having an adjustable secondary tap is supplied from an appropriateexternal alternating current line source, and is connected to the inputterminals of a rectifier 57, from the output terminals of which arectified DC. potential of, say, 24 volts is thus taken, and an overloadfuse 58 is placed in one of the rectifier output leads. Theelectromagnet coil 14 and the solenoid coil 33 0f the unit 10 areparalleled across the output leads, each in series with the contact of acontrol relay. The relays are respectively designated 6t) and 61, withthe series connected contacts designated by corresponding referencenumerals.

Relays 60, 61 for the electromagnet and solenoid coils 14-, 33,respectively, are alternating current relays and are connected inparallel across the AC. supply leads 62 of the system in the interlockarrangement shown. Thus, a limit switch 63, mounted on the die member 11and closed momentarily on the down stroke of the latter, near the bottomof the stroke, is shunted by a contact of the magnet coil relay 60, witha further limit switch 64 in series. The limit switch 64 is mounted onthe scrap receiver 53, being actuated when the receiver is underneaththe die member 11. Switch 64 has two contacts, one of which de-energizesthe electromagnet coil circuit and the other of which energizes thesolenoid coil circuit, being connected in series across the leads 62with the coil of solenoid control relay 61.

What We claim as our invention is:

1. An electromagnetic unit of the type described, comprising anelectromagnet housing receiving a coil and having means to mount thehousing to an outer side portion of a moving part, in lateral referenceto the direction of movement of the latter, a solenoid housing fixedlymounted in superposed relation to said electromagnet housing, anannular, non-magnetic spacer between said housings, a solenoid coil insaid solenoid housing, a core movable axially in said solenoid housingin response to energization of its coil, said core projecting into saidspacer, and a stripping member movable axially in said electromagnethousing and projecting into said spacer at one end, said strippingmember being actuated by said core upon energization of said solenoidcoil to project at its opposite end from said electromagnet housing,said electromagnet housing and part having parallel exposed workengaging surfaces in substantially flush, side-by-side relation to oneanother.

2. An electromagnetic unit of the type described, comprising anelectromagnet housing receiving a coil and having means to mount thehousing to an outer side portion of a moving part, in lateral referenceto the direction of movement of the latter, a solenoid housing fixedlymounted in superposed relation to said electromagnet housing, anannular, non-magnetic spacer between said housings, a solenoid coil insaid solenoid housing, a core movable axially in said solenoid housingin response to energization of its coil, said core projecting into saidspacer, a stripping member movable axially in said electromagnet housingand projecting into said spacer at one end, said stripping member beingactuated by said core upon energization of said solenoid coil to projectat its opposite end from said electromagnet housing, and means foradjusting the actuating stroke of said stripping member, saidelectromagnet housing and part having parallel exposed work engagingsurfaces in substantially flush, side-by-side relation to one another.

3. An electromagnetic unit of the type described, comprising anelectromagnet housing receiving a coil and having means to mount thehousing to an outer side portion of a moving part, in lateral referenceto the direction of movement of the latter, a solenoid housing fixedly m4 AAA mounted in superposed relation to said electromagnet housing, anannular, non-magnetic spacer between said housings, a solenoid coil insaid solenoid housing, a core movable axially in said solenoid housingin response to energization of its coil, said core having a plungerthreadedly engaged thereon and projecting into said spacer, and astripping member movable axially in said electromagnet housing andprojecting into said spacer at one end, said stripping member beingactuated by said plunger upon energization of said solenoid coil toproject at its opposite end from said electromagnet housing, saidelectromagnet housing and part having parallel exposed work engagingsurfaces in substantially flush, side-by-side relation to one another.

4. A dual acting, electromagnetic handling unit for sheet metal blankingpresses and the like, comprising an electromagnet having a corepresenting a flat Work holding surface of substantial area movable toengage with a sheet to be blanked, a stripper mounted for movement insaid core in the direction in which said surface moves to engage thesheet, a solenoid housing in superposed relation to said core, saidstripper having an actuating plunger core received in said solenoidhousing, a solenoid coil in said housing' surrounding said plunger corein encircling relation to the latter and effective upon energization toproject said plunger core and stripper axially, said stripper beingreceived substantially wholly within said first named core when not soprojected and extending substantially outwardly of said surface of thelatter when so projected, and an electrical circuit including means toperiodically energize said solenoid coil in timed relation to theengagement of said first named core surface with a sheet and cause saidstripper to eject said sheet from said first named core.

5. A dual acting, electromagnetic handling unit for sheet metal blankingpresses and the like, comprising an electrically energized electromagnethaving a magnetizable core presenting a flat work holding surface ofsubstantial area movable to engage with a sheet to be blanked, astripper mounted for movement in said core in the direction in whichsaid surface moves to engage the sheet, a coil operatively arrangedrelative to said core to magnetize the latter upon energization of saidcoil, a solenoid housing in superposed relation to said core, anon-magnetic spacer interposed between and secured to said core andhousing, said stripper having an actuating plunger core and beingreceived through said spacer into said solenoid housing, a solenoid coilin said housing surrounding said plunger core and effective uponenergization to project said plunger core and stripper axially, saidstripper being received substantially wholly within said electromagnetcore when not so projected and extending substantially outwardly, ofsaid surface of the latter when so projected, and an electrical circuitincluding means electrically connected to said respective coils toenergize the same in alternation, whereby to alternately cause saidelectromagnet core to grip and hold a sheet upon energization and tocause said stripper to eject said sheet from said first named core uponenergization of said solenoid coil.

6. An electromagnetic unit for use in association with a press in theblanking of pieces from sheet stock and the handling of the blankedstock, comprising an electromagnet housing, an electrically energizableelectromagnetcoil in said housing, said housing having means to mountthe same to a moving part of the press, and having a bottom surfaceadapted to be disposed, as so mounted, in flush relation to a bottomsurface of said press part, a solenoid housing fixedly mounted insuperposed relation to said electromagnet housing and having anelectrically energizable solenoid coil therein, and stripping meansmovable in said housings and having a stock engaging portion which isprojected beneath the bottom surface of said electromagnet housing todisengage the stock from the latter by and upon energization of saidsolenoid coil, said stock engaging portion being movable upon engagementof said press part and electromagnet housing with said sheet stock intoa position not to project substantially beneath said bottom surface ofthe electromagnet housing, and means to electrically energize saidcoils.

7. An electromagnetic unit for use in association with a press in theblanking of pieces from sheet stock and the handling of the blankedstock, comprising an electromagnet housing, an electrically energizableelectromagnet coil in said housing, said housing having means to mountthe same to a moving part of the press and having a bottom surfaceadapted to be disposed, as so mounted, in flush relation to a bottomsurface of said press part, a solenoid housing fixedly mounted insuperposed relation to said electromagnet housing and having anelectrical-1y energizable solenoid coil therein, a solenoid core movablein said solenoid housing coaxially of said solenoid coil and actuable bythe latter in response to energization of the last named coil, astripping member movable in said electromagnet housing coaxially of saidcore and actuable by said core to project the stripping member beneathsaid bottom surface of said electromagnet housing, said stripping memberbeing movable upwardly upon engagement of said press part andelectromagnet housing with said sheet stock into a position in which itdoes not project substantially beneath said bottom surface of theelectromagnet housing, and means to electrically energize said coils.

8. An electromagnetic unit for use in association with a press in theblanking of pieces from sheet stock and the handling of the blankedstock, comprising an electromagnet housing, an electrically energizableelectromagnet coil in said housing, said housing having means to mountthe same to an outer side portion of a moving part of the press, andbeing shaped to be in flush relation to said side portion as so mounted,said housing having a bottom surface adapted to be disposed as somounted in flush relation to a bottom surface of said press part, asolenoid housing fixedly mounted in superposed relation to saidelectromagnet housing and having an electrically energizable solenoidcoil therein, a solenoid coil movable in said solenoid housing coaxiallyof said solenoid coil and actuable by the latter in response toenergization of the last named coil, a stripping member movable in saidelectromagnet housing coaxially of said core and actuable by said coreto project the stripping member beneath said bottom surface of saidelectromagnet housing, said stripping member being movable upwardly uponengagement of said press part and electromagnet housing with said sheetstock into a position in which it does not project substantially beneathsaid bottom surface of the electromagnet housing, and means toelectrically energize said coils in alternation and in timed relation tothe movement of said press part to initially attract the sheet stock\from which a part has been blanked to said bottom surface of theelectromagnet housing and subsequently strip the same from saidelectromagnet housing.

9. An electromagnetic unit for use in association with a press in theblanking of pieces from sheet stock and the handling of the blankedstock, comprising an electromagnet housing, an electrically energizableelectromagnet coil in said housing, said housing having means to mountthe same to a moving part of the press and having a bottom surfaceadapted to be disposed as so mounted in flush relation to a bottomsurface of said press part, a solenoid housing fixedly mountedsuperposed relation to said electromagnet housing and having anelectrically energizable solenoid coil therein, a solenoid core movablein said solenoid housing coaxially of said solenoid coil and actuable bythe latter in response to energization of the last named coil, anannular, nonmagnetic spacer interposed between said housings, said coreprojecting axially into said spacer, a stripping member movable in saidelectromagnet housing coaxially of said core and extending axially intosaid spacer for actuation by said core to project the stripping memberbeneath said bottom surface of said electromagnet housing, saidstripping member being movable upwardly upon engagement of said presspart and electromagnet housing with said sheet stock into a position inwhich it does not project substantially beneath said bottom surface ofthe electromagnet housing, and means to electrically energize said coilsin alternation and in timed relation to the movement of said press partto initially attract the sheet stock from which a part has been blankedto said bottom surface of the electromagnet housing and subsequentlystrip the same from said electromagnet housing.

10. An electromagnetic unit for use in association with a press in theblanking of pieces from sheet stock and the handling of the blankedstock, comprising an electromagnet housing, an electrically energizableelectromagnet coil in said housing, said housing having means to mountthe same to an outer side portion of a moving part of the press, andbeing shaped to be in flush relation to said side portion as so mounted,said housing having a bottom surface adapted to be disposed as somounted in llush relation to a bottom surface of said press part, asolenoid housing fixedly mounted in superposed relation to saidelectromagnet housing and having an electrically energizable solenoidcoil therein, a solenoid core movable in said solenoid housing coaxiallyof said solenoid coil and actuable by the latter in response toenergization of the last named coil, an annular, non-magnetic spacerinterposed between said housings, said core projecting axially into saidspacer, a stripping member movable in said electromagnet housingcoaxially of said core and extending axially into said spacer foractuation by said core to project the stripping member beneath saidbottom surface of said electromagnet housing, said stripping memberbeing movable upwardly upon engagement of said press part andelectromagnet housing with said sheet stock into a position in which itdoes not project substantially beneath said bottom surface of theelectromagnet housing, and means to electrically energize said coils inalternation and in timed relation to the movement of said press part toinitially attract the sheet stock from which a part has been blanked tosaid bottom surface of the electromagnet housing and subsequently stripthe same from said electromagnet housing.

11. The combination with a press for the blanking of pieces from sheetstock, of an electromagnet unit for the handling of the blanked stock,said unit comprising an electromagnet housing, an electricallyenergizable electromagnet coil in said housing, said housing havingmeans to mount the same to a moving part of the press and having abottom surface adapted to be disposed as so mounted in flush relation toa bottom surface of said press part, a solenoid housing fixedly mountedin superposed relation to said electromagnet housing and having anelectrically energizable solenoid coil therein, a solenoid core movablein said solenoid housing coaxially of said solenoid coil and actuable bythe latter in response to energization of the last named coil, astripping member movable in said electromagnet housing coaxially of saidcore and actuable by said core to project the stripping member beneathsaid bottom surface of said electromagnet housing, said stripping memberbeing movable upwardly upon engagement of said press part andelectromagnet housing with said sheet stock into a position in which itdoes not project substantially beneath said bottom surface of theelectromagnet housing, and means to electrically energize said coils.

12. The combination with a press for the blanking of pieces from sheetstock, of an electromagnet unit for the handling of the blanked stock,said unit comprising an electromagnet housing, an electricallyenergizable electromagnet coil in said housing, said housing havingmeans to mount the same to an outer side portion of a moving part of thepress, and being shaped to be in flush relation to said side portion asso mounted, said housing having a bottom surface adapted to. be disposedas so mounted in flush relation to a bottom surface of said press part,a solenoid housing fixedly mounted in superposed relation to saidelectromagnet housing and having an electrically energizable solenoidcoil therein, a solenoid core movable in said solenoid housing coaxiallyof said solenoid coil and actuable by the latter in response toenergization of the last named coil, an annular, non-magnetic spacerinterposed between said housings, said core projecting axially into saidspacer, a stripping member movable in said electromagnet housingcoaxially of said core and extending axially into said spacer foractuation by said core to project the stripping member beneath saidbottom surface of said electromagnet housing, said stripping memberbeing movable upwardly upon engagement of said press part andelectromagnet housing with said sheet stock into a position in which itdoes not project substantially beneath said bottom surface of theelectromagnet housing, and means to electrically energize said coils inalternation and in timed relation to the movement of said press part toinitially attract the sheet stock from which a part has been blanked tosaid bottom surface of the electromagnet housing and subsequently stripthe same from said electromagnet housing.

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